This application is based upon and claims benefit of priority of Japanese Patent Application No. 2000-208833 filed on Jul. 10, 2000, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a meter driven by a driving unit having a stepping motor, the meter including an illuminated pointer.
2. Description of Related Art
A meter for use in an automotive instrument panel having an illuminated pointer is disclosed in JP-A-9-21655. The meter includes a scale plate, a light-guiding plate disposed behind the scale plate in parallel therewith, a wiring board disposed behind the light-guiding plate in parallel therewith, and a driving unit attached to the rear surface of the wiring board. A pointer rotating in front of the upper surface of the scale plate is connected to the driving unit via a pointer shaft extending through holes provided in the scale plate, the light-guiding plate and the wiring board. Plural light emitting diodes (LED) disposed on the upper surface of the wiring board in the vicinity of the pointer shaft emit light toward the light-guiding plate and the pointer.
Usually, the driving unit includes a stepping motor having a magnet rotor and a stator yoke with coil units. Coil ends of the coil units are electrically connected to the wiring board around the pointer shaft. Since the LEDs are also positioned in the vicinity of the pointer shaft, the wiring board around the pointer shaft is congested with both electrical connections for the coil ends and the LEDs. If the coil ends are positioned at a vicinity of the pointer shaft with priority, the location of the LEDs is restricted and light cannot be uniformly emitted through a pointer shaft hole.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved meter in which the coil ends are electrically connected to the wiring board at positions apart from the pointer shaft, around which illuminating light sources are positioned, to avoid wiring congestion around the pointer shaft.
In a meter, such as a meter for use in an automotive instrument panel, a pointer is driven by a driving unit disposed behind a scale plate. A wiring board is placed between the scale plate and the driving unit. Plural light sources such as light emitting diodes for illuminating the pointer are positioned on the wiring board in the vicinity of a pointer shaft. The driving unit includes a stepping motor having coil units and a magnet rotor.
Terminal pins for supplying electric current to the coil units are disposed on the wiring board and soldered to a current supply circuit formed on the wiring board. The terminal pins are placed apart from the light sources positioned around the pointer shaft to avoid wiring congestion in the vicinity of the pointer shaft.
The driving unit includes a reduction gear train for reducing rotational speed of the stepping motor and for transferring its rotational force to the pointer shaft. Alternatively, the pointer shaft may be directly driven by the stepping motor. A light-guiding plate may be disposed behind the scale plate, so that the light emitted from the light sources illuminates not only the pointer but also the scale plate. In the case the scale plate is illuminated, the scale plate is made of a transparent material.
Since the terminal pins for supplying electric current to the stepping motor coil units are positioned on the wiring board apart from the light sources, the light sources can be properly positioned around the pointer shaft in the vicinity thereof. Therefore, the light from the light sources is uniformly distributed around the pointer shaft with high luminance.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.